Process for producing a cast resin coil

ABSTRACT

For the production of a cast resin coil consisting of a plurality of axially superimposed flat coils, it is proposed that the corresponding flat coils be first of all produced by winding a first inner partial winding and a second outer partial winding with the interposition of individual spacer members by which sector-shaped intervening spaces are formed. The individual flat coils are then placed together axially and oriented so that their intervening spaces coincide, thus forming axial cooling channels. Moldings are inserted into each of said channels. This is followed by the encapsulation of the assembled flat coils. After the curing of the casting resin, the moldings are removed from the cooling channels. A cast resin coil produced in this manner has an impregnable layer of material, preferably in the region of the cooling channels by which the wall thickness of the cooling channels is predetermined in relation to the corresponding strip conductors.

BACKGROUND OF THE INVENTION

The present invention relates generally to processes for producing acast resin coils,and more particulary to a cast resin coil that consistsof a plurality of flat coils superimposed axially on each other, and acast resin coil thus produced.

German Utility Model 71 26 814 discloses a winding for a transformerwhich consists of axially superimposed individually wound flat coils.The individual flat coils have intervening spaces between their innerand outer partial windings which lie coaxially one within the other. Thepartial windings can be wound continuously from the same conductors. Theintervening spaces of the corresponding flat coils form, in thisconnection, axial cooling channels. The winding can be encapsulated incasting resin. It has been found in practice that the encapsulating ofthe flat coils is very problematical. No solution for this problem isindicated in the German Utility Model.

Up to the present time, therefore, an inner cast resin coil and an outercast resin coil were produced separately, then placed coaxially onewithin the other and mechanically connected to each other so that aconcentric cooling channel was present between the two cast resin coils.

From U.S. Pat. No. 4,129,938 a process is known for producing anencapsulated winding of wire conductor having cooling channels. For thispurpose, after a predetermined number of inner windings, an impregnablenon-woven fabric is first of all placed on the winding. Thereupon,moldings which form cooling channels are placed on and an additionallayer of the impregnable non-woven fabric is placed over this. An outerpartial winding is then applied. The entire winding is encapsulated, themoldings being removed after the encapsulation. Axial cooling channelswhich are distributed uniformly over the circumference are then producedin the winding. This known winding technique, however, cannot be used inan arrangement consisting of a plurality of flat coils, since themoldings used in the individual flat coils were difficult to remove.Furthermore, the alignment of the intervening spaces of the individualflat coils with respect to each other is difficult.

From British 936 380, there is known the use of a non-woven fabric andof moldings for the forming of cooling channels for transformer coils.

The exact development of the coil, particularly in the transfer regionof the coaxially arranged individual coils, is not taken up in any ofthe documents mentioned.

The present invention is directed to the problem of developing animproved process for producing windings that have cooling channels andare built of several flat coils. The present invention is also directedto the problem of developing an improved cast resin coil with stripconductors.

SUMMARY OF THE INVENTION

The present invention solves the first problem; producing flat coils bywinding a first winding consisting of one or more conductors, and thenwinding one or more additional partial windings on the first winding,wherein the one or more partial windings are wound continuously from thesame conductor, or conductors; using individual spacers to formsector-shaped intervening spaces; axially superimposing the flat coilsand aligning the sector-shaped intervening spaces, thus forming axialcooling channels; disposing at least one molding into each coolingchannel; encapsulating the superimposed flat coils, wherein the thusencapsulated individual spacers form stiffening webs between the partialwindings; removing the moldings from the cooling channels; and applyinga layer of impregnable material to the partial windings beforeencapsulating them, at least in the circumferential sections lyingbetween the spacers, wherein the transfer of the conductor or conductorsfrom the first partial winding to the one or more additional partialwindings occurs in a connecting web between two adjacent spacers. Inthis way, a practical process is provided by which the cast resin coilcan be produced. A coil produced by this process is characterized byhigh mechanical strength as well as good cooling action. In particular,flat coils having a plurality of concentrically arranged sector-shapedcooling channels can easily be produced by this process. In this way,cooling the flat coils during operation is substantially improved.

It is favorable if, prior to the encapsulation, a layer of impregnablematerial is applied to the partial windings at least in thecircumferential sections lying between the spacer members. This can bedone, for instance, by wrapping a non-woven fabric over its entirecircumference. In this way, on the one hand, the partial windings inquestion are protected from injury when the molding is introduced and,on the other hand, a precisely defined wall thickness of the coolingchannels for the partial windings is obtained, whereby, in turn, animprovement in the insulation values is produced. Since no separatingfoils are used for the insulation, no additional potential boundarysurfaces are produced on either wall of the cooling channel.

If the corresponding flat coils with their partial windings are woundcontinuously from a signal subsequent connecting of said partialwindings is unnecessary. It is preferred to employ the process with astrip conductor, which may consist for example of copper or aluminum.The a cast resin coil produced by the method of the present invention

The present invention solves the other problem by providing a cast resincoil produced by the method of the present invention. Such a cast resincoil has only very little stress in the cooling channel since only aslight winding stress is present between the partial windings at thecooling channel which are preferably wound continuously from a stripconductor. In this way, the wall thickness of the cooling channel can bemade particularly thin which, in its turn, contributes to improvedcooling. In this way, material is also saved, so that the weight of thecoil is reduced.

Furthermore, the flat coils of the present invention may have greatlydiffering forms. For example, disc coils or square coils can be used inthe present invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross section through a cast resin coil, with

FIG. 2 is a longitudinal section through the cast resin coil of FIG. 1,along the line II--II.

DETAILED DESCRIPTION

The cross section in FIG. 1 is taken in the plane of a conductor whichcan be developed as a strip conductor or wire conductor. The cast resincoil has a first inner partial winding 3 and a second outer partialwinding 5, which windings are arranged concentrically to each other. Theinner partial winding 3 can, in this case, be arranged on a coil formeror else be wound in self-supporting manner.

On the circumference of the inner partial winding 3, a layer ofimpregnable material 7a can, if desired, be applied (showed in dashedline). Adjoining it in radial direction there are furthermore first ofall spacer members 11, 11a, 11b, another layer of material 7b and theouter partial winding 5. Mats of glass fiber which have a thicknesspredetermined by their manufacture are for instance suitable as layer7a, 7b. The spacer members 11, 11a, 11b are so arranged on the innerpartial winding 3 that they form sector-shaped intervening spaces 8between the inner and outer windings 3 and 5. The thickness of thespacer members 11 determines, in this connection, the distance betweenthe partial windings 3 and 5. A plurality of intervening spaces 8 lyingaxially alongside of each other form in each case a cooling channel 9.The layers of material 7a and 7b determine in this connection the wallthickness of the cooling channel 9 for the conductor of thecorresponding partial winding 3, 5.

In the present example, the partial windings 3 and 5 are woundcontinuously from a single conductor 13a. In this connection, windingcan also be effected in two layers, the second layer 13b being possiblyan insulating layer or another conductor which is insulated from theconductor 13a. The intervening spaces 8 are sector-shaped portions of acircular ring. The conductor 13 is extended outward in a known a mannerat an end part 14 of the cast resin coil 1 at which a connecting element15 is arranged. A connecting of the conductor 13a within the end part 14to other conductors is also possible.

The spacer members 11, 11a, 11b can also be arranged directly betweenthe partial windings 3 and 5 without the interpositioning of a layer ofmaterial 7a, 7b so that the layers of material 7a, 7b rest against thepartial windings 3 and 5 only in the region of the intervening spaces 8.

The cast resin coil 1 shown in FIG. 2 is formed of a plurality of flatcoils 17 placed alongside of each other which are wound, for instance,from a strip conductor. The flat coils 17 can also be wound from a wireconductor.

The individual flat coils 17 are superimposed axially, in whichconnection spacer parts 19 can be inserted between the individual flatcoils 17 (as shown in dashed line). It can be noted in the embodimentshown that the layers of material 7a, 7b extend only over the axialwidth of the flat coils 17. On the other hand, if the layers of material7a, 7b are introduced subsequently into the sector-shaped interveningspaces formed by the spacer bodies 11a, 11b, of the already superimposedflat coils, the layers of material 7a, 7b can extend also over theentire length of the arrangement (development similar to the spacinglayer 20).

Such a cast resin coil 1 has a very high mechanical strength since thepartial windings 3 and 5 are no longer mechanically connected to eachother individually as in the prior art but, rather, form a structuralunit. In particular, however, the electrical strength is improved,particularly in the region of the cooling channels 9 using a respect tothe partial windings 3 and 5. This applies, in particular, to anembodiment with strip conductor since, in such case, only a slightwinding tension is still present between the partial windings 3 and 5,which permits a reduction of the wall thickness of the cooling channel9. In this way, however, an improved cooling of the partial windings 3and 5 is also possible.

The partial windings of the flat coils 17 can be wound continuously froma conductor 13a, so that no additional expense for external connectionis necessary. The transfer of the conductor 13a from the inner partialwinding 3 to the outer partial winding 5 takes place preferably in theregion of the spacer members 11a, 11b, the regions forming connectingwebs 21 between the partial windings 3 and 5 after the encapsulation.The transfers of the individual conductors of the corresponding flatcoils 17 can, in this case, be arranged in each case one web apart incircumferential direction. In this way, stresses between the transferscan also be reduced. The radial height of the cooling channels 9 isdetermined essentially by the spacer members 11, 11a, 11b. This heightlies within the range of 5 to 50 mm, and preferably within the range of10 to 20 mm. Ledges are suitable as spacer member 11, 11a, 11b, whichledges also may have a profile for guiding the moldings. More than twopartial windings 3, 5 can also be arranged concentrically to each other,cooling channels then being arranged in each case between the adjacentpartial windings.

The following procedure can be used for the production of a cast resincoil:

The individual flat coils 17 are first of all produced. For thispurpose, a first partial winding 3 is wound from one or more conductors13a and, one or more partial windings 5 are wound on it, in each casewith the interpositioning of individual spacer members 11, 11a, 11b.

The spacer members 11, 11a, 11b are in this connection so arranged,distributed over the circumference of the first partial winding 3, thatsector-shaped intervening spaces 8 having the shape of portions of acircular ring are formed. This arranging can be effected during thewinding process. If a predetermined number of flat coils 17 is produced,they are superimposed axially, the intervening spaces 8 being aligned incoincidence with each other and forming axial cooling channels 9. Asalready described above, in this connection the winding transfers of theconductor 13a from flat coil 17 to flat coil 17 can be arranged, spacedfrom each other, in circumferential direction. Thereupon, at least onemolding is inserted in each cooling channel 9, the molding extendingaxially over the entire length of the subsequent cast resin coil,whereby the flat coils 17 are additionally aligned and fixed inposition. The moldings used may be discardable or reusable. Their shapeis predetermined in accordance with the shape of the cooling channeldesired. The cooling channels 9 are sealed from the penetration ofcasting resin, particularly at their open ends.

This is followed by the encapsulating of the assembled flat coils 17 inknown manner. For this purpose, the assembled flat coils 17 arearranged, together with the moldings, in an encapsulating mold andencapsulated with a casting resin. This is effected by the means andprocess generally known to the person skilled in the art. After theencapsulation and the curing of the encapsulation material, theencapsulation mold and the moldings are removed. If the moldings arereusable, they can for instance be knocked or pressed out. Discardablemoldings can be removed, for instance, by destruction or heating.

Prior to the encapsulation, the impregnable layer of material ispreferably applied to the partial windings 3 and 5 at least in thecircumferential sections lying between the spacer members 11, 11a, 11b(as already described above). The layer of material 7a, 7b can, however,also be applied after the flat coils 17 have been placed together bylining the cooling channels 9 with the layer of material 7a, 7b. Thiscan possibly be effected also with the aid of the moldings onto whichthe layer of material is laid.

We claim:
 1. A process for producing a cast resin coil comprising a plurality of axially superimposed flat coils each of the flat coils including an inner winding, an outer winding, and a plurality of spacers disposed between the inner and outer windings thereby defining a plurality of sector-shaped intervening spaces between the inner and outer windings, said method comprising the steps of:a) producing a first flat coil by:winding a first inner winding using a first conductive element; disposing a first plurality of spacers; winding a first outer winding from said first conductive element; applying a first layer of impregnable material between the first inner and outer windings in a first plurality of circumferential sections between each of the first plurality of spacers; and transferring the first conductive element from the first inner winding to the first outer winding in a first connecting web between two of the first plurality of spacers; b) producing a second flat coil by:winding a second inner winding using a second conductive element; disposing a second plurality of spacers; winding a second outer winding from said second conductive element; applying a second layer of impregnable material between the second inner and outer windings in a second plurality of circumferential sections between each of the second plurality of spacers; and transferring the second conductive element from the second inner winding to the second outer winding in a second connecting web between two of the second plurality of spacers; c) axially superimposing said first and second flat coils; d) aligning said first and second plurality of sector-shaped intervening spaces thereby forming a plurality of axial cooling channels; e) disposing a molding into each of the plurality of axial cooling channels; f) encapsulating the superimposed first and second flat coils, whereby the first and second plurality of spacers form stiffening webs between the inner and outer windings when encapsulated; and g) removing every molding from the plurality of axial cooling channels after encapsulation.
 2. The method according to claim 1, further comprising the steps of applying a first additional layer of impregnable material on an inner circumferential surface of the first outer winding before encapsulation, and applying a second additional layer of impregnable material on an inner circumferential surface of the second outer winding before encapsulation, wherein said steps of applying first and second layers of impregnable material further comprise applying the first and second layers of impregnable material to an outer circumferential surface of the first and second inner windings, respectively.
 3. The method according to claim 1, wherein the first and second conductive elements comprise strip conductors.
 4. The method according to claim 2, wherein the first and second conductive elements comprise strip conductors.
 5. The method according to claim 1, wherein the first conductive element comprises a first plurality of conductors, the second conductive element comprises a second plurality of conductors, and the first and second inner and outer windings are wound from the first and second plurality of conductors, respectively.
 6. The method according to claim 2, wherein the first conductive element comprises a first plurality of conductors, the second conductive element comprises a second plurality of conductors, and the first and second inner and outer windings are wound from the first and second plurality of conductors, respectively.
 7. The method according to claim 1, wherein the first conductive element comprises a first plurality of strip conductors, the second conductive element comprises a second plurality of strip conductors, and the first and second inner and outer windings are wound from the first and second plurality of strip conductors, respectively.
 8. A process for producing a cast resin coil comprising a plurality of axially superimposed flat coils each of the flat coils including an inner winding, an outer winding, and a plurality of spacers disposed between the inner and outer windings thereby defining a plurality of sector-shaped intervening spaces between the inner and outer windings, said method comprising the steps of:a) producing a plurality of flat coils by:winding an inner winding using a conductive element; disposing a plurality of spacers; winding an outer winding from said conductive element; applying a layer of impregnable material between the inner and outer windings in a plurality of circumferential sections between each of the plurality of spacers; and transferring the conductive element from the inner winding to the outer winding in a connecting web between two of the plurality of spacers; b) axially superimposing said plurality of flat coils; c) aligning each of said plurality of sector-shaped intervening spaces, whereby a plurality of axial cooling channels are formed; d) disposing a molding into each of the plurality of axial cooling channels; e) encapsulating the superimposed plurality of flat coils, whereby the plurality of spacer members form stiffening webs between the inner and outer windings when encapsulated; and f) removing every molding from the plurality of axial cooling channels after encapsulation.
 9. The method according to claim 8, further comprising the step of applying an additional layer of impregnable material on an inner circumferential surface of the outer winding of each of the plurality of flat coils, wherein said step of applying the layer of impregnable material further comprises applying the layer of impregnable material to an outer circumferential surface of the inner winding.
 10. The method according to claim 8, wherein the conductive element for each of the plurality of flat coils comprises a strip conductor.
 11. The method according to claim 9, wherein the conductive element for each of the plurality of flat coils comprises a strip conductor.
 12. The method according to claim 8, wherein the conductive element for each of the plurality of flat coils comprises a plurality of strip conductors, and the inner and outer windings of each of the plurality of flat coils are wound from the plurality of strip conductors.
 13. The method according to claim 9, wherein the conductive element for each of the plurality of flat coils comprises a plurality of strip conductors, and the inner and outer windings of each of the plurality of flat coils are wound from the plurality of strip conductors.
 14. A process for producing a cast resin coil comprising a plurality of axially superimposed flat coils each flat coil including an inner winding, an outer winding, and a plurality of spacers disposed between the inner and outer windings thereby defining a plurality of sector-shaped intervening spaces between the inner and outer windings, said method comprising the steps of:a) producing a plurality of flat coils by:winding an inner winding using a conductive element; disposing a plurality of spacers; and winding an outer winding from said conductive element; transferring the conductive element from the inner winding to the outer winding in a connecting web between two of the plurality of spacers; b) axially superimposing said plurality of flat coils; c) aligning each of said plurality of sector-shaped intervening spaces, whereby a plurality of axial cooling channels are formed; d) applying a layer of impregnable material at least on an outer and an inner circumferential surface of each of said plurality of axial cooling channels; e) disposing a molding into each of the plurality of axial cooling channels; f) encapsulating the superimposed plurality of flat coils, whereby the plurality of spacer members form stiffening webs between the inner and outer windings when encapsulated; and g) removing every molding from the plurality of axial cooling channels after encapsulation. 